The present invention relates generally to sectional doors which move between a closed vertical position and an open horizontal position. More particularly, the present invention relates to a non-binding sectional door and a method of assembly which compensates for the bowing of sectional door panels during movement between the vertical and horizontal positions. More specifically, the present invention relates to a door and method for locating the hinges between panels of such sectional doors to whereby the adjacent panels do not contact and bind when moving on tracks between the closed vertical position and the open horizontal position.
It is known that sectional door panels of the type employed in garages or other buildings that move between a closed vertical position and an open horizontal position will necessarily deflect or sag when in the open horizontal position. This is because of the panel construction and the fact that the panels are supported in such position solely by rollers at each end of the panels. When two adjacent panels are both in the horizontal position in the horizontal track sections, there is potentially no problem, inasmuch as the sag at the adjacent panel edges is essentially identical. Similarly, there is essentially no problem when adjacent panels are in the vertical closed position, as there is essentially no sag in a direction perpendicular to the face of the panel. A problem arises, however, when adjacent panels are passing through the curved transition track section between the vertical section and the horizontal section. In that instance, the horizontally disposed panel is approaching its maximum deflection while the adjacent panel in the curved transition track section is undergoing a substantially lesser deflection which may produce rubbing contact or even binding at the mating edges of the panels. The extent of this deflection varies with the angular position relative to vertical of adjacent panels passing through the curved transition track section.
While it is impractical to totally eliminate deflection in such sectional door panels, the amount of deflection varies greatly depending upon the width of the door, the thickness of the surface material, the presence or absence of a backer, the presence or absence of foamed reinforcement, and the presence or absence and design of rails, struts or other reinforcing members proximate the panel edges. Normally, deflection or sagging is most critical in pan doors without any of the strengthening or reinforcing features alluded to above. Absent unusual reinforcing in a door panel, the maximum deflection is normal to the face of the door at substantially the center point intermediate the panel ends. Industry specifications indicate that the deflection or sagging can be up to {fraction (1/120)} of the door width and be considered acceptable. Thus, in the case of a standard 16 foot double car door, the deflection can be as much as approximately 41 mm and remain within industry standards.
For a number of years, it was common to employ door edge profiles with varying gaps in the panel to adjacent panel interfaces. This was accomplished with the use of flexible hinges or other constructions which permit varying the gaps between the panel at differing locations during their travel between the closed vertical position and the open horizontal position. In other instances, the panel-to-panel edges develop greater spacing therebetween when adjacent panels are at greater angularity, as when passing through the curved transition track section between the vertical track sections and the horizontal track sections. With this type of a varying gap panel spacing as a function of relative adjacent panel angularity, the deflection can be accommodated without binding or even rubbing or other contact between adjacent panel edges.
More recently, the design of the section interfaces have gone to pinch resistant configurations which will neither allow fingers to be inserted in the interface nor allow the interface to close down on fingers by maintaining a clearance or gap of less then 9 millimeters at all times during door movement. Even more desirably, maintaining the clearance or gap at less then 4 millimeters prevents pinching the skin such as to create a xe2x80x9cblood blisterxe2x80x9d. Since these pinch resistant configurations must maintain a minimal clearance or gap throughout its operating range such creates a serious problem in efforts to design an anti-pinch door without the inherent sag or deflection of the door panels producing rubbing or binding of the mating joints. This is because the deflection can greatly exceed the required and desired clearance for pinch resistant configurations.
In the instances of pinch resistant designs, binding can be encountered to an extent that an undesirable amount of force is required to move the panel interfaces through the curved transition track section for a door. Further, the force varies at different locations through the transitional track section and is not constant, such that it creates a surging condition in door operation. The surging can be recognized as erratic movement caused by rapid acceleration and deceleration of the door motion during its travel between the closed vertical position and the horizontal open position. Doors which employ openers or operators often use a control system that monitors force required to move the door as a function of door travel as a method to determine entrapment may be unable to respond to the surging of the door or the additional force required to overcome binding. This may result in false stops where a control system senses entrapment of a foreign object or other erratic operation of the control system and thus, the motorized operation of the door.
Thus, there remains a need for a non-binding door design which does not possess the reinforcing features and attendant costs normally associated with pinch resistant doors.
Accordingly, it is an object of the present invention to provide a sectional door wherein the panel interfaces maintain a minimal gap during movement between a closed vertical position and an open horizontal position satisfying pinch resistant specifications. Another object of the present invention is to provide such a sectional door which eliminates rubbing and possible binding between interfaces of adjacent panels even during moving through the curved transition track section between the vertical track section and the horizontal track section. An additional object of the invention is to provide such a sectional door that eliminates or at least minimizes surging such that successful use with conventional powered openers or operators and control systems therefor is assured. A further object of the present invention is to provide such a sectional door wherein the clearance or gap between the joints of adjacent sections be maintained with a gap or clearance of less than 1 millimeter without rubbing or binding during movements between the closed vertical position and open horizontal position of the door.
Another object of the present invention is to provide a sectional door which has essentially minimal constant gap panel interfaces which do not require special design profiles on the joints forming the interfaces between adjacent panels. Yet another object of the present invention is to provide such a sectional door which does not require the presence of rub strips or barriers at the interfaces between adjacent panels. Another object of the present invention is to provide such a sectional door which does not require any additional or modified components. A further object of the present invention is to provide such a door which is readily operable with counterbalance systems, operators or openers, and control systems that are conventionally designed for a door configuration.
It is yet another object of the present invention to provide such a sectional door which can exceed both mandatory and desired pinch resistant specifications recognized in the industry. A further object of the present invention is to provide such a sectional door having no additional manufacturing costs above those for a comparable door not incorporating the present invention. Yet a further object of the present invention is to provide such a sectional door which does not require any additional labor input to effect the manufacture, assembly, or installation of doors embodying the present invention as compared with an identical conventional door.
In general, the present invention contemplates a sectional door movable between a closed vertical position and an open horizontal position having, a series of adjacent panels, each of the panels having an upper joint member and a lower joint member, the lower joint member having a configuration to establish a clearance with the configuration of the upper joint member of an adjacent panel during angular articulation of the adjacent panels in moving between the closed vertical position and the open horizontal position, end hinge assemblies located proximate the longitudinal ends of the panels and connecting the adjacent panels at a first pivot axis, and at least one center hinge assembly connecting the adjacent panels at a second pivot axis offset from the first pivot axis, whereby a portion of the clearance is maintained irrespective of variations in the deflection of the panels in moving between the closed vertical position and the open horizontal position.